Surgical knife with controllably extendable blade and gauge therefor

Abstract

Surgical knife with controllably extendable blade, the blade retained by a blade holder extending through an axial opening in the knife body and connected with a member threadedly retained within the knife body for axial adjustment and also connected to an adjustment knob at the rear end of the knife. Another feature of the knife is a foot configuration which facilitates precise use and control of the knife. Preferably the invention also comprises the knife, as disclosed, in combination with a gauge for visually inspecting blade projection, the gauge indicator consisting of a pair of eccentric circles or portions thereof, the blade projection being measured by comparison with the radial distance between the two circles.

We claim: 
     
       1. Surgical knife with controllably extendable blade comprising: (a) a generally cylindrical body with a front end, a rear end, axially displaced therefrom, and a centrally disposed axial opening along the length thereof;   (b) a blade disposed at the front end of said body in a plane which includes the axis of said body;   (c) a blade holder having said knife blade secured at the front end thereof, said holder extending rearwardly from said front end along the axis of said body to a distal end disposed within said body, said holder being freely movable along said axis, said holder further including, at its distal end, a cam surface perpendicular to said axis;   (d) a foot, having a frontal surface fixed with respect to said body, and a central axial opening being aligned and in communication with said central axial opening of said body;   (e) means for restraining said holder from angular movement about said axis;   (f) means for urging said holder rearwardly along said axis;   (g) a generally cylindrical adjustment knob, a section of which overlaps a section of said body and is rotatable thereabout and slidable therealong   (h) a cam member having a front cam projection in contact with said distal end cam surface of said blade holder, said cam member extending rearwardly thereof along said axis and being urged rearwardly by said urging means while permitting relative rotational movement between said cam projection and said cam surface;   (i) means for fastening said cam member to said knob;   (j) holder positioning means threadedly secured within said body for longitudinal adjustment of said holder positioning means relative to said body along said axis by rotational adjustment of said positioning means; and   (k) selective means for permitting limited axial movement of said holder, cam member and knob relative to said holder positioning means at either one of two fixed axially spaced positions;   (l) means for coupling rotational movement of said knob to cause corresponding rotational movement of said holder positioning means so that when said holder, cam member and knob are at one of said fixed axially spaced positions, relative to said holder positioning means, the longitudinal position of said blade, relative to said body, is adjusted by rotational movement of said knob.   
     
     
       2. Surgical knife, as recited in claim 1, further including means for determining the length of said blade projecting out from said foot frontal surface. 
     
     
       3. Surgical knife, as recited in claim 1, wherein said retaining means (e) comprises at least one radial projection and a mating slot in which said projection is slidingly engaged, said projection and said slot being disposed at radially opposed locations on said blade holder and on the inner surface of said body. 
     
     
       4. Surgical knife, as recited in claim 3, said blade holder further including an enlarged diameter section slidingly engaged in said body axial opening. 
     
     
       5. Surgical knife, as recited in claim 1, said blade holder further including an enlarged diameter section slidingly engaged in said body axial opening. 
     
     
       6. Surgical knife, as recited in claim 4, wherein the opposed location on said holder is disposed on said enlarged diameter section. 
     
     
       7. Surgical knife, as recited in any one of claims 3, 5, or 6, said body opening including a reduced diameter section forward of said enlarged diameter section of said blade holder and said urging means (f) comprises a spring compressed between said reduced diameter opening section and said enlarged diameter holder section. 
     
     
       8. Surgical knife, as recited in any one of claims 1, 2, 3, 4, 5, or 6, wherein said selective means (k) comprises an axially aligned bayonet slot on a rearward cylindrical extension of said positioning means surrounding said cam member, said slot including, at its forward and rear ends, short circumferential extensions, and a mating bayonet projection on said cam member slidingly engaged in said bayonet slot. 
     
     
       9. Surgical knife, as recited in claim 2, wherein said length determining means comprises calibrated markings on adjacent portions of the outer surface of said body and said knob, said markings indicating the relative axial position of said body and said blade. 
     
     
       10. Surgical knife, as recited in claim 9, wherein said retaining means (e) comprises at least one radial projection and a mating slot in which said projection is slidingly engaged, said projection and said slot being disposed at radially opposed locations on said blade holder and on the inner surface of said body. 
     
     
       11. Surgical knife, as recited in claim 10, said blade holder further including an enlarged diameter section slidingly engaged in said body axial opening, said body opening including a reduced diameter section forward of said enlarged diameter section of said blade holder and said urging means (f) comprises a spring compressed between said reduced diameter opening section and said enlarged diameter holder section. 
     
     
       12. Surgical knife, as recited in claim 1, said blade having two parallel side surfaces, and leading and trailing edges, said edges being parallel to said body axis, and a cutting edge extending rearwardly from said trailing edge to said leading edge and forming angular intersections therewith, characterized in that said foot opening comprises a first axial slot segment aligned with and slightly spaced from said blade rearwardly of said frontal surface, said slot opening extending and being open to the outer periphery of said foot along the trailing edge of said blade, and a second essentially circular opening segment rearwardly of said first segment, said foot, in the plane of said blade sides having a profile which includes a cutaway portion, exposing in said profile, a portion of said blade trailing edge, rearwardly of said frontal surface, when said blade is in its operating position. 
     
     
       13. Surgical knife, as recited in claim 8, wherein said length determining means comprises calibrated markings on adjacent portions of the outer surface of said body and said knob, said markings indicating the relative axial position of said body and said blade, said blade having two parallel side surfaces, and leading and trailing edges, said edges being parallel to said body axis, and a cutting edge extending rearwardly from said trailing edge to said leading edge and forming angular intersections therewith, characterized in that said foot opening comprises a first axial slot segment aligned with and slightly spaced from said blade rearwardly of said frontal surface, said slot opening extending and being open to the outer periphery of said foot along the trailing edge of said blade, and a second essentially circular opening segment rearwardly of said first segment, said foot, in the plane of said blade sides having a profile which includes a cutaway portion, exposing in said profile, a portion of said blade trailing edge, rearwardly of said frontal surface, said frontal surface comprising a planar surface extending from a first line at or just radially outward from said blade trailing edge to a second line radially inward from said first line. 
     
     
       14. Surgical knife with controllably extendable blade comprising: (a) a generally cylindrical body with a front end, a rear end, axially displaced therefrom, and a centrally disposed axial opening along the length thereof;   (b) a blade disposed at the front end of said body in a plane which includes the axis of said body; and   (c) a foot, having a frontal surface fixed with respect to said body, and a central axial opening being aligned and in communication with said central axial opening of said body, said blade having two parallel side surfaces, and leading and trailing edges, said edges being parallel to said body axis, and a cutting edge extending rearwardly from said trailing edge to said leading edge and forming angular intersections therewith, characterized in that said foot opening comprises a first axial slot segment aligned with and slightly spaced from said blade rearwardly of said frontal surface, said slot opening extending and being open to the outer periphery of said foot along the trailing edge of said blade, and a second essentially circular opening segment rearwardly of said first segment, said foot, in the plane of said blade sides, having a profile which includes a cutaway portion, exposing in said profile, a portion of said blade trailing edge, rearwardly of said frontal surface.   
     
     
       15. Surgical knife, as recited in claim 14, said frontal surface comprising a planar surface extending from a first line at or just radially outward from said blade trailing edge to a second line radially just inward from said first line. 
     
     
       16. Surgical knife, as recited in claim 15, wherein the front most projection of said foot includes said frontal surface and a second surface intersecting said frontal surface at said second line, said second surface sloping rearwardly away therefrom.